Project Summary Infertility is a common complication of endometriosis; while IVF successfully treats endometriosis-associated infertility, pregnancy rates are diminished compared to other etiologies of infertility. Our long- term objectives are to better identify and treat endometriosis related infertility. Our central hypothesis is that in infertile woman with endometriosis undergoing in vitro fertilization-embryo transfer (IVF-ET), live birth rates will improve in those pretreated with GnRH antagonist compared to placebo. The use of gonadotropin releasing hormone (GnRH) agonist prior to IVF has been suggested to improve success, however studies have been small and rarely reported live birth rates. Further, use of this approach is limited by the long treatment time required. Recent approval of an oral GnRH antagonist for endometriosis provides a novel option for women with endometriosis who are undergoing IVF. This agent avoids parenteral administration and the prolonged delay in initiation of action as was seen with GnRH agonists. There have been no studies on the efficacy of GnRH antagonists for the treatment of endometriosis-related infertility. We propose a randomized clinical trial of oral GnRH antagonist pre-treatment for women with endometriosis who are undergoing IVF, with a primary outcome of live birth rate. We have also recently demonstrated aberrant micoRNAs in the circulation of women with endometriosis, a panel of which we have subsequently validated as a biomarker with high sensitivity and specificity for the detection of active disease. We secondarily propose that disease biomarkers will identify women who will benefit from GnRH antagonist pre-treatment, allowing a precision medicine approach to endometriosis-related infertility. The proposed study is significant due to the common occurrence of both infertility and endometrioses as well as the lack of precision in both diagnosis and therapy. We use an innovative approach to identify endometriosis as well as a novel intervention designed to improve the prognosis of women with endometriosis undergoing IVF.